Akira was only ever seen while he was under the influence of the drug Trigger. When he was seen, however, he was incredibly aggressive to essentially everything that was around him, attacking buildings and civilians. He was very confident in his abilities, believing himself to be totally indestructible and undefeatable. However, he was capable of showing some sort of sanity. He was also capable of displaying fear when he realized he was in danger.

As this manga does not have an anime, their is no exact voice for him. He is a young adult, who's 25. If you could please give him a medium-to-deeper pitched voice, that would be great! You will also need to use a raspier, deeper voice for when he turns into his bigger, tougher form.